24
"
 1 - Create new group:
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 sudo groupadd <new_group>
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 2 - Add users to it:
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 sudo usermod -a -G <new_group> <user1>
 sudo usermod -a -G <new_group> <user2>
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 3 - Set new permissions:
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 sudo chgrp -R <new_group> /path/to/the/directory
 sudo chmod -R 770 /path/to/the/directory
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 "